Synthesis of homo polymers and block copolymers of chiral/achiral phenylacetylene derivatives. Spectroscopic and molecular modeling study on solvent‐dependent predominance of helical sense

A chiral acetylene monomer, (S)‐4‐(2‐butoxy)phenylacetylene [(S)‐1] and an achiral acetylene monomer, 4‐propoxyphenylacetylene (2) were block copolymerized using [(nbd)Rh{C(Ph)=CPh2}(PPh3)]/PPh3 as a catalyst to obtain chiral‐first/achiral‐second and achiral‐first/chiral‐second block copolymers, poly[(S)‐1]‐block‐poly(2) and poly(2)‐block‐poly[(S)‐1]. The block copolymers exhibited circular dichroism (CD) signals in THF attributable to helical conformation with predominantly one‐handed screw sense originating from the poly[(S)‐1] block. In CHCl3, the block copolymers exhibited CD signals with signs reversed from those in THF. The conformational stability of the copolymers was dependent on the composition of (S)‐1 units, regardless of the feed order of the chiral and achiral monomers. The solvent‐dependent predominance of helical sense was confirmed by the molecular dynamics (MD) simulations of poly[(S)‐1] 32‐mer models.